A magnetoresistive sensor layer structure for laser annealing

Abstract

The embodiment of the present application discloses a kind of magnetoresistive sensor layer structures for laser annealing, comprising: substrate;Magnetic resistance sensing unit is located on substrate, and antiferromagnetic pinning layer or permanent magnetic bias layer is included in magnetic resistance sensing unit;Top heat-absorbing layer located above magnetic resistance sensing unit and / or bottom heat-absorbing layer located below magnetic resistance sensing unit, the product of the volume specific heat density of top heat-absorbing layer is greater than the product of the volume specific heat density of top electrode layer, the product of the volume specific heat density of bottom heat-absorbing layer is greater than the product of the volume specific heat density of bottom electrode layer, when the write temperature of antiferromagnetic pinning layer or permanent magnetic bias layer is higher than the respective corresponding blocking temperature or Curie temperature, the temperature of bottom electrode layer and top electrode layer is lower than the respective corresponding melting point temperature;Laser absorption layer and laser transparent layer.The embodiment of the present application can solve the problem that electrode layer is easy to ablate.

Description

Technical Field

[0001] This invention relates to the field of magnetic sensor technology, and more particularly to a magnetoresistive sensor layer structure for laser annealing. Background Technology

[0002] Magnetoresistive sensors, such as magnetic tunnel junction sensors, can use an antiferromagnetic material layer as a pinning layer. In this case, annealing in a magnetic field is used to obtain the magnetic field-sensitive direction of the magnetic tunnel junction at a temperature higher than its blocking temperature. For magnetic tunnel junctions that use a permanent magnet bias layer to bias the reference layer or free layer, magnetic field annealing at a temperature higher than its Curie temperature is performed to obtain the magnetization direction of the permanent magnet material.

[0003] When laser annealing is used, the laser scans the magnetoresistive sensing unit array on the magnetoresistive sensor die, allowing for the acquisition of magnetoresistive sensing units with different sensitivity directions. This enables the fabrication of a multi-axis magnetoresistive sensor on a single die, which is of great significance for the design, manufacturing, and use of magnetoresistive sensors.

[0004] However, in the multilayer structure of a magnetoresistive sensor, the overall structure of the bottom electrode layer / magnetically sensitive unit stack layer / top electrode layer is extremely thin, almost nanometer-thick. Furthermore, gaps exist between adjacent magnetic tunnel junctions, with electrical connections only between the top or bottom electrode layers. Therefore, under a fixed laser power and scanning speed, due to the difference in heat capacity between the materials at the magnetic tunnel junctions and the gaps, when the antiferromagnetic pinning layer or permanent magnet bias layer at the magnetic tunnel junction heats to above the critical blocking temperature or Curie temperature, the top or bottom electrode layer at the gap may heat to above its material melting point, resulting in ablation and causing the magnetoresistive sensor to burn out. Summary of the Invention

[0005] This invention provides a magnetoresistive sensor layer structure for laser annealing to solve the problem that existing magnetoresistive sensor layer structures are prone to ablation during laser annealing.

[0006] This invention provides a magnetoresistive sensor layer structure for laser annealing, comprising:

[0007] Substrate;

[0008] A magnetoresistive sensing unit located on the substrate, the magnetoresistive sensing unit comprising, from bottom to top, a seed layer, a bottom electrode layer, a magnetic sensing unit stack layer and a top electrode layer, the magnetic sensing unit stack layer comprising at least an antiferromagnetic nailing layer or a permanent magnet bias layer;

[0009] The top heat-absorbing layer located above the magnetoresistive sensing unit and / or the bottom heat-absorbing layer located below the magnetoresistive sensing unit, wherein the volume of the top heat-absorbing layer is... Specific heat The product of densities is greater than the volume of the top electrode layer. Specific heat The product of densities, the volume of the bottom heat-absorbing layer Specific heat The product of densities is greater than the volume of the bottom electrode layer. Specific heat The product of densities means that when the writing temperature of the antiferromagnetic nailing layer or the permanent magnet bias layer is higher than their respective blocking temperature or Curie temperature, the temperatures of the bottom electrode layer and the top electrode layer are both lower than their respective melting point temperatures.

[0010] A laser absorption layer is located above the magnetoresistive sensing unit;

[0011] A laser-transparent layer is located above the laser-absorbing layer.

[0012] In this embodiment of the invention, a heat-absorbing layer is provided on at least one of the top and bottom sides of the magnetoresistive sensing unit, and the volume of the top heat-absorbing layer is... Specific heat The product of densities is greater than the volume of its nearest neighboring top electrode layer. Specific heat The product of densities, the volume of the bottom heat-absorbing layer Specific heat The product of densities is greater than the volume of its nearest neighboring bottom electrode layer. Specific heat The product of densities results in an endothermic layer with a specific heat much higher than that of the magnetoresistive sensing unit. This allows for maximum homogenization of the specific heat among the film, top electrode, and bottom electrode layers of the magnetoresistive sensing unit, reducing the temperature rise differences caused by the specific heat differences among these layers. Consequently, when the writing temperature of the antiferromagnetic pinning layer / permanent magnet bias layer reaches its blocking temperature / Curie temperature, the temperature rise of the bottom and top electrode layers is similar, and both temperatures remain below their respective melting points. Based on this, ablation of the magnetoresistive sensor layer structure during laser annealing can be avoided, improving the stability and laser annealing efficiency of the magnetoresistive sensor layer structure. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, although the drawings described below are some specific embodiments of the present invention, those skilled in the art can extend and extend the basic concepts of the device structure, driving method and manufacturing method disclosed and indicated by various embodiments of the present invention to other structures and drawings. Undoubtedly, these should all be within the scope of the claims of the present invention.

[0014] Figure 1 This is a schematic diagram of a magnetoresistive sensor layer structure provided in an embodiment of the present invention;

[0015] Figure 2 This is a schematic diagram of another magnetoresistive sensor layer structure provided in an embodiment of the present invention;

[0016] Figure 3 This is a schematic diagram of another magnetoresistive sensor layer structure provided in an embodiment of the present invention;

[0017] Figure 4 This is a topological diagram of the top heat-absorbing layer of the magnetoresistive sensor layer structure;

[0018] Figure 5 for Figure 4 Topological diagram of the top heat-absorbing layer of a single-arm magnetoresistive sensor layer structure;

[0019] Figure 6 for Figure 4 Topological diagram of the top heat-absorbing layer of a push-pull multi-arm magnetoresistive sensor layer structure;

[0020] Figure 7 This is a topological diagram of the top heat-absorbing layer of another magnetoresistive sensor layer structure;

[0021] Figure 8 for Figure 7 Topological diagram of the top heat-absorbing layer of a single-arm magnetoresistive sensor layer structure;

[0022] Figure 9 for Figure 7 Topological diagram of the top heat-absorbing layer of the push-pull multi-arm magnetoresistive sensor layer structure;

[0023] Figure 10 This is a topological diagram of the top heat-absorbing layer of another magnetoresistive sensor layer structure.

[0024] Figure 11 for Figure 10 Topological diagram of the top heat-absorbing layer of a single-arm magnetoresistive sensor layer structure;

[0025] Figure 12 for Figure 10 Topological diagram of the top heat-absorbing layer of the push-pull multi-arm magnetoresistive sensor layer structure;

[0026] Figure 13 This is a topological diagram of the top heat-absorbing layer of another magnetoresistive sensor layer structure.

[0027] Figure 14 for Figure 13 Topological diagram of the top heat-absorbing layer of a single-arm magnetoresistive sensor layer structure;

[0028] Figure 15 for Figure 13 Topological diagram of the top heat-absorbing layer of the push-pull multi-arm magnetoresistive sensor layer structure. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the basic concepts disclosed and indicated in the embodiments of this invention, all other embodiments obtained by those skilled in the art are within the scope of protection of this invention.

[0030] This invention provides a magnetoresistive sensor layer structure for laser annealing. The magnetoresistive sensor layer structure includes: a substrate; a magnetoresistive sensing unit located on the substrate, the magnetoresistive sensing unit comprising, from bottom to top, a seed layer, a bottom electrode layer, a magnetoresistive unit stack layer, and a top electrode layer, the magnetoresistive unit stack layer comprising at least an antiferromagnetic nailing layer or a permanent magnet bias layer; a top heat-absorbing layer located above the magnetoresistive sensing unit and / or a bottom heat-absorbing layer located below the magnetoresistive sensing unit, the volume of the top heat-absorbing layer being... Specific heat The product of densities is greater than the volume of the top electrode layer. Specific heat The product of densities, the volume of the bottom heat-absorbing layer Specific heat The product of densities is greater than the volume of the bottom electrode layer. Specific heat The product of densities means that when the write temperature of the antiferromagnetic pinning layer or the permanent magnet bias layer is higher than their respective blocking temperature or Curie temperature, the temperatures of the bottom electrode layer and the top electrode layer are both lower than their respective melting point temperatures; the laser absorption layer is located above the magnetoresistive sensing unit; the laser transparency layer is located above the laser absorption layer.

[0031] In this embodiment of the invention, a heat-absorbing layer is provided on at least one of the top and bottom sides of the magnetoresistive sensing unit, and the volume of the top heat-absorbing layer is... Specific heat The product of densities is greater than the volume of its nearest neighboring top electrode layer. Specific heat The product of densities, the volume of the bottom heat-absorbing layer Specific heat The product of densities is greater than the volume of its nearest neighboring bottom electrode layer. Specific heat The product of densities results in an endothermic layer with a specific heat much higher than that of the magnetoresistive sensing unit. This allows for maximum homogenization of the specific heats of the film, top electrode, and bottom electrode layers of the magnetoresistive sensing unit, reducing the temperature rise differences caused by the differences in specific heats among these layers. Consequently, when the writing temperature of the antiferromagnetic pinning layer / permanent magnet bias layer reaches its blocking temperature / Curie temperature, the temperature rises of the bottom and top electrode layers are similar, and both temperatures remain below their respective melting points. Based on this, ablation of the magnetoresistive sensor layer structure during laser annealing can be avoided, improving the stability and laser annealing efficiency of the magnetoresistive sensor layer structure.

[0032] The optional substrate has a passivation layer on the side of the substrate facing the magnetoresistive sensing unit, and the thermal conductivity of the passivation layer is lower than that of the seed layer. 1 / 10.

[0033] The materials for the top or bottom heat absorption layer can be tantalum, titanium, copper, molybdenum, gold, silver, aluminum, platinum, or tin.

[0034] The optional material for the laser absorption layer is carbon black, or a non-magnetic laser-absorbing resin containing carbon black, or a laser-absorbing coating.

[0035] The optional materials for the laser transparent layer are ZrO2, Ti3O5, Ta2O5, HfO2, ZnS, ZnSe, Al2O3, MgO, MgF2, SiO2, YbF3, or AlF3.

[0036] The thickness of the optional top or bottom heat-absorbing layer is determined by the power of the external laser annealing and the heating time.

[0037] Optionally, along the bottom-up direction, the top heat-absorbing layer covers the top electrode layer and the bottom electrode layer, and the top heat-absorbing layer and the top electrode layer are electrically isolated;

[0038] The top heat-absorbing layer includes a first region and a second region. The first region overlaps with the bottom electrode layer but does not overlap with the top electrode layer. The second region overlaps with the top electrode layer. An insulating material is filled between the top heat-absorbing layer and the top electrode layer. The first region and the second region are in electrical contact.

[0039] Optionally, the top heat-absorbing layer further includes a third region, which does not overlap with either the top electrode layer or the bottom electrode layer, and is electrically in contact with both the first region and the second region.

[0040] Optionally, along the bottom-up direction, the top heat-absorbing layer covers the top electrode layer and the bottom electrode layer, and there is electrical contact between the top heat-absorbing layer and the top electrode layer;

[0041] The top heat absorption layer includes a first region and a second region. The first region overlaps with the bottom electrode layer but does not overlap with the top electrode layer, while the second region overlaps with the top electrode layer. The first region and the second region are electrically isolated from each other.

[0042] Optionally, the top heat-absorbing layer further includes a third region, which does not overlap with the top electrode layer and the bottom electrode layer, and is electrically isolated from the first region and the second region.

[0043] Optionally, along the bottom-to-top direction, the bottom heat-absorbing layer covers the top electrode layer and the bottom electrode layer, and the bottom heat-absorbing layer and the bottom electrode layer are electrically isolated;

[0044] The bottom heat-absorbing layer includes a fourth region and a fifth region. The fourth region overlaps with the bottom electrode layer but does not overlap with the top electrode layer. The fifth region overlaps with the bottom electrode layer. An insulating material is filled between the bottom heat-absorbing layer and the bottom electrode layer. The fourth region and the fifth region are in electrical contact.

[0045] Optionally, the bottom heat-absorbing layer further includes a sixth region, which does not overlap with either the top electrode layer or the bottom electrode layer, and is electrically in contact with the fourth region and the fifth region, respectively.

[0046] Optionally, along the bottom-to-top direction, the bottom heat-absorbing layer covers the top electrode layer and the bottom electrode layer, and there is electrical contact between the bottom heat-absorbing layer and the bottom electrode layer;

[0047] The bottom heat absorption layer includes a fourth region and a fifth region. The fourth region overlaps with the bottom electrode layer but does not overlap with the top electrode layer, while the fifth region overlaps with the bottom electrode layer. The fourth region and the fifth region are electrically isolated from each other.

[0048] Optionally, the bottom heat absorption layer further includes a sixth region, which does not overlap with the top electrode layer and the bottom electrode layer, and is electrically isolated from the fourth region and the fifth region, respectively.

[0049] It should be noted that the description above of the heat-absorbing layer covering the electrode layer along the bottom-to-top direction essentially refers to the projection of the heat-absorbing layer along the bottom-to-top direction covering the projection of the electrode layer along the bottom-to-top direction. Further details will not be elaborated upon below.

[0050] The above are the main solutions provided by the embodiments of the present invention. The magnetoresistive sensor layer structure provided by the embodiments of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] refer to Figure 1 The diagram shown is a schematic representation of a magnetoresistive sensor layer structure provided in an embodiment of the present invention. Figure 1As shown, the magnetoresistive sensor layer structure 1(0) includes a top heat-absorbing layer 13 disposed above the top electrode layer 7. Specifically, the magnetoresistive sensor layer structure 1(0) includes, from bottom to top, at least a substrate 2, a passivation layer 3, a magnetoresistive sensing unit 41, a top heat-absorbing layer 13, a laser absorption layer 8, and a laser transparency layer 9. Among them, the magnetoresistive sensing unit 41 includes, from bottom to top, a seed layer 4, a bottom electrode layer 5, a magnetic sensing unit stack layer 6, and a top electrode layer 7. The magnetic sensing unit stack layer 6 includes at least an antiferromagnetic nail layer or a permanent magnet bias layer 5(0).

[0052] The substrate 2 is typically a silicon wafer, but is not limited to this. The passivation layer 3 is optionally a low thermal conductivity insulating layer, which serves to prevent heat from being conducted to the substrate 2. In this case, the thermal conductivity of the passivation layer 3 can be 1 / 10 of the thermal conductivity of the seed layer 4, provided that the stability of the magnetoresistive sensor layer structure is ensured.

[0053] In the magnetoresistive sensor layer structure 1(0), the magnetoresistive sensing units 41 are interconnected through the bottom electrode layer 5 and the top electrode layer 7. Insulating material 10 is filled between the magnetoresistive sensing units 41 in the magnetoresistive sensor layer structure 1(0) for insulation between the magnetoresistive sensing units 41. Insulating material 10 is also filled between the magnetoresistive sensing units 41 and the top heat-absorbing layer 13 in the magnetoresistive sensor layer structure 1(0) to achieve electrical isolation.

[0054] The magnetoresistive sensor layer structure 1(0) is annealed using a laser, wherein the laser spot 11 scans horizontally on the surface of the magnetoresistive sensor layer structure 1(0) in the scanning direction 12.

[0055] refer to Figure 2 The diagram shown is a schematic of another magnetoresistive sensor layer structure provided in an embodiment of the present invention. Figure 2 As shown, the magnetoresistive sensor layer structure 1(1) includes a bottom heat-absorbing layer 14 disposed below the bottom electrode layer 5. Specifically, the magnetoresistive sensor layer structure 1(1) includes at least a substrate 2, a passivation layer 3, a bottom heat-absorbing layer 14, a magnetoresistive sensing unit 41, a laser absorption layer 8, and a laser transparency layer 9 from bottom to top. Figure 2 and Figure 1 The same parts will not be repeated.

[0056] In the magnetoresistive sensor layer structure 1(1), an insulating material 10 is filled between the magnetoresistive sensing unit 41 and the bottom heat absorption layer 14 to achieve electrical isolation.

[0057] refer to Figure 3 The diagram shown is a schematic representation of another magnetoresistive sensor layer structure provided in an embodiment of the present invention. Figure 3As shown, the magnetoresistive sensor layer structure 1(2) includes a bottom heat-absorbing layer 14 disposed below the bottom electrode layer 5 and a top heat-absorbing layer 13 disposed above the top electrode layer 7. Specifically, the magnetoresistive sensor layer structure 1(2) includes, from bottom to top, at least a substrate 2, a passivation layer 3, a bottom heat-absorbing layer 14, a magnetoresistive sensing unit 41, a top heat-absorbing layer 13, a laser absorption layer 8, and a laser transparency layer 9. Figure 3 and Figure 1 The same parts will not be repeated.

[0058] In the magnetoresistive sensor layer structure 1(2), an insulating material 10 is filled between the magnetoresistive sensing unit 41 and the top heat-absorbing layer 13 to achieve electrical isolation. In the magnetoresistive sensor layer structure 1(2), an insulating material 10 is filled between the magnetoresistive sensing unit 41 and the bottom heat-absorbing layer 14 to achieve electrical isolation.

[0059] It can be seen that, Figure 1 In the magnetoresistive sensor layer structure, the magnetoresistive sensor layer structure 1(0) has three different material structure regions, namely region A, region B and region C. Among them, the material structure of region A is: laser transparent layer 9 / laser absorption layer 8 / top heat absorption layer 13 / insulating material 10 / bottom electrode layer 5 / seed layer 4; the material structure of region B is: laser transparent layer 9 / laser absorption layer 8 / top heat absorption layer 13 / insulating material 10 / top electrode layer 7 / magnetic sensitive unit stacked layer 6 / bottom electrode layer 5 / seed layer 4; the material structure of region C is: laser transparent layer 9 / laser absorption layer 8 / top heat absorption layer 13 / insulating material 10 / top electrode layer 7 / insulating material 10.

[0060] exist Figure 2 In the magnetoresistive sensor layer structure, magnetoresistive sensor layer structure 1(1) has three different material structure regions, namely region A, region B and region C. Among them, the material structure of region A is: laser transparent layer 9 / laser absorption layer 8 / insulating material 10 / bottom electrode layer 5 / seed layer 4 / insulating material 10 / bottom heat absorption layer 14; the material structure of region B is: laser transparent layer 9 / laser absorption layer 8 / insulating material 10 / top electrode layer 7 / magnetic sensitive unit stacked layer 6 / bottom electrode layer 5 / seed layer 4 / insulating material 10 / bottom heat absorption layer 14; the material structure of region C is: laser transparent layer 9 / laser absorption layer 8 / insulating material 10 / top electrode layer 7 / insulating material 10 / bottom heat absorption layer 14.

[0061] exist Figure 3In the magnetoresistive sensor layer structure, the magnetoresistive sensor layer structure 1(2) has three different material structure regions, namely region A, region B and region C. Among them, the material structure of region A is: laser transparent layer 9 / laser absorption layer 8 / top heat absorption layer 13 / insulating material 10 / bottom electrode layer 5 / seed layer 4 / insulating material 10 / bottom heat absorption layer 14; the material structure of region B is: laser transparent layer 9 / laser absorption layer 8 / top heat absorption layer 13 / insulating material 10 / top electrode layer 7 / magnetic sensitive unit stacked layer 6 / bottom electrode layer 5 / seed layer 4 / insulating material 10 / bottom heat absorption layer 14; the material structure of region C is: laser transparent layer 9 / laser absorption layer 8 / top heat absorption layer 13 / insulating material 10 / top electrode layer 7 / insulating material 10 / bottom heat absorption layer 14.

[0062] During the laser annealing stage, the laser heats the material instantaneously, and the heat is conducted from the upper surface of the magnetoresistive sensor layer structure to its lower surface.

[0063] Without the heat-absorbing layer, the different material structures of regions A, B, and C result in different volumes in different regions of the magnetoresistive sensor layer structure. Specific heat Different density products result in different heat transfer efficiencies and temperature rise effects, which in turn cause the temperatures in regions A and C to exceed the melting points of the bottom electrode layer 5 and the top electrode layer 7, leading to damage in regions A and C.

[0064] In this embodiment of the invention, a bottom heat-absorbing layer 14 and / or a top heat-absorbing layer 13 are added, and the volume of the top heat-absorbing layer 13 is increased. Specific heat The product of densities is greater than the volume of its corresponding top electrode layer 7. Specific heat The product of densities, the volume of the bottom heat-absorbing layer 14 Specific heat The product of densities is greater than the volume of its corresponding bottom electrode layer 5. Specific heat The product of densities. Assuming the magnetic sensor stack 6 includes an antiferromagnetic pin layer 5(0), when the write temperature of the antiferromagnetic pin layer 5(0) is higher than its blocking temperature, the temperature of the bottom electrode layer 5 is lower than its melting point temperature, and the temperature of the top electrode layer 7 is lower than its melting point temperature. Alternatively, assuming the magnetic sensor stack 6 includes a permanent magnet bias layer 5(0), when the write temperature of the permanent magnet bias layer 5(0) is higher than its Curie temperature, the temperature of the bottom electrode layer 5 is lower than its melting point temperature, and the temperature of the top electrode layer 7 is lower than its melting point temperature, thus avoiding damage to the magnetoresistive sensor layer structure.

[0065] The following statement is based on specific principles and formulas.

[0066] Using a simple one-dimensional heat conduction model, the temperature rise of the material is expressed as equation (1):

[0067] (1);

[0068] Where △T is the temperature rise (unit: °C), P is the laser power (unit: W), t is the heating time (unit: s), m is the material mass (unit: kg), and Cv is the specific heat of the material (unit: J / (kg·°C)).

[0069] For regions A and C containing only one type of material, the calculation is as follows:

[0070] The mass of the material, m, is expressed as equation (2): m = ρ·V (2);

[0071] Where ρ is density (unit: kg / m³) 3 V is the heating volume (unit: m³). 3 );

[0072] The heating volume V is expressed as equation (3): V = W·h·d (3);

[0073] Where W is the width of region A, region B, or region C, h is the thickness of region A, region B, or region C, and d is the diameter of the laser spot.

[0074] For regions A, B, and C where multiple materials are introduced, the calculations are as follows:

[0075] The total heating volume V is expressed by equation (4): V = Σ i V i (4);

[0076] The total material mass M is expressed by equation (5): M = Σ i ρ i ·V i (5);

[0077] The density ρ is expressed as equation (6): ρ = M / V (6);

[0078] Average material specific heat Represented as equation (7): (7).

[0079] Without a heat-absorbing layer in the magnetoresistive sensor layer structure, the material characteristics and temperature rise results of regions A, B, and C are described in Tables 1 to 4 below.

[0080] Table 1 shows the material characteristics and temperature rise results for regions A, B, and C.

[0081] Table 1

[0082]

[0083] As shown in Table 1 above, the laser annealing conditions are assumed to be: blocking temperature Tb = 350℃, laser power P = 5W, laser spot diameter d = 25µm, and heating time t = dwell time = 0.1µs.

[0084] Assuming the dimensions of each layer in the magnetoresistive sensing unit are:

[0085] Seed layer / bottom electrode layer (Ta): 0.15µm thick, 15µm wide;

[0086] Top electrode layer (Cu): 1.00 μm thick, 10 μm wide;

[0087] Magnetic sensitive unit stacked layer (NiFe main): thickness 0.50um, width 5um.

[0088] For a magnetoresistive sensing unit composed of a seed layer / bottom electrode layer / magnetic sensing unit stack layer / top electrode layer, the materials in different regions are as follows: the magnetoresistive sensing unit material in region A is mainly Ta, the magnetoresistive sensing unit material in region C is mainly Cu, and the magnetoresistive sensing unit material in region B is mainly a composite material Ta / main NiFe / Cu.

[0089] As shown in Table 1, during the laser annealing stage, when the temperature of the composite material Ta / NiFe / Cu in region B reaches 394℃, it is close to the blocking temperature Tb=350℃ of the antiferromagnetic nail layer. At this time, the temperature of region A reaches 3903℃, exceeding the melting point temperature of the bottom electrode layer Ta (3017℃), and the temperature of region C reaches 613℃, which is lower than the melting point of Cu (1084℃). Obviously, region A will undergo ablation, causing the entire magnetoresistive sensor layer structure to malfunction.

[0090] To reduce the temperature in region A, the thickness of the seed layer / bottom electrode layer was increased to 200 nm. Table 2 shows the material characteristics and temperature rise results for another region A, region B, and region C.

[0091] Table 2

[0092]

[0093] As shown in Table 2 above, assuming the dimensions of each layer in the magnetoresistive sensing unit are:

[0094] Seed layer / bottom electrode layer (Ta): 0.20 μm thick, 15 μm wide;

[0095] Top electrode layer (Cu): 1.00 μm thick, 10 μm wide;

[0096] Magnetic sensitive unit stacked layer (NiFe main): thickness 0.50um, width 5um.

[0097] As shown in Table 2, during the laser annealing stage, when the temperature of the composite material Ta / NiFe / Cu in region B reaches 375℃, it is close to the blocking temperature Tb=350℃ of the antiferromagnetic nail layer. At this time, the temperature of region A reaches 2933℃, which is lower than the melting point of Ta (3017℃), and the temperature of region C reaches 613℃, which is lower than the melting point of Cu (1084℃). Although region A will not undergo ablation, its temperature is still close to the melting point of the bottom electrode layer Ta, making it prone to ablation.

[0098] If the thickness of the seed layer / bottom electrode layer is further increased to 250 nm, Table 3 shows the material characteristics and temperature rise results for another region A, region B and region C.

[0099] Table 3

[0100]

[0101] As shown in Table 3 above, assuming the dimensions of each layer in the magnetoresistive sensing unit are:

[0102] Seed layer / bottom electrode layer (Ta): 0.25 μm thick, 15 μm wide;

[0103] Top electrode layer (Cu): 1.00 μm thick, 10 μm wide;

[0104] Magnetic sensitive unit stacked layer (NiFe main): thickness 0.50um, width 5um.

[0105] As shown in Table 3, during the laser annealing stage, when the temperature of the composite material Ta / NiFe / Cu in region B reaches 360℃, it is close to the blocking temperature Tb=350℃ of the antiferromagnetic nail layer. At this time, the temperature in region A reaches 2351℃, which is further lower than the melting point of Ta (3017℃), and the temperature in region C reaches 613℃, which is lower than the melting point of Cu (1084℃). Although region A will not undergo ablation, the temperature difference between regions A, B, and C is still very large.

[0106] Increasing the thickness of the top electrode layer to 1.1 μm, Table 4 shows the material characteristics and temperature rise results for regions A, B, and C.

[0107] Table 4

[0108]

[0109] As shown in Table 4 above, assuming the dimensions of each layer in the magnetoresistive sensing unit are:

[0110] Seed layer / bottom electrode layer (Ta): 0.25 μm thick, 15 μm wide;

[0111] Top electrode layer (Cu): 1.10 μm thick, 10 μm wide;

[0112] Magnetic sensitive unit stacked layer (NiFe main): thickness 0.50um, width 5um.

[0113] As shown in Table 4, during the laser annealing stage, when the temperature of the composite material Ta / NiFe / Cu in region B reaches 341℃, it is below the blocking temperature Tb=350℃ of the antiferromagnetic nail layer. At this time, the temperature in region A reaches 2351℃, which is below the melting point of Ta (3017℃), and the temperature in region C reaches 559℃, which is below the melting point of Cu (1084℃). However, the composite material in region B cannot reach the blocking temperature, and therefore cannot complete the laser writing operation of the magnetoresistive sensing unit.

[0114] As can be seen from Tables 1 to 4 above, the method of simply increasing the film thickness of the magnetoresistive sensing unit is very inefficient.

[0115] Based on this, a heat-absorbing layer is added to the magnetoresistive sensor layer structure. The material characteristics and temperature rise results of regions A, B and C are described in Table 5 below.

[0116] Table 5

[0117]

[0118] As shown in Table 5, for example, a top heat absorption layer is added to regions A, B, and C. The material of the top heat absorption layer is Cu, and the thickness is 2 μm.

[0119] It can be seen that when the composite material temperature in region B reaches 429℃, the laser power increases to 20W. However, the temperature in region A decreases to 563℃, and the temperature in region C decreases to 492℃. The temperatures in regions A, B, and C are very close, far below the melting points of the top and bottom electrode layers. Although the laser power increases to 20W, this increase can be achieved simply by adjusting the laser parameters.

[0120] Based on this, a heat-absorbing layer is introduced, and the specific heat of the heat-absorbing layer... density With a volume of 3328, it is much larger than the bottom electrode layer (214), the top electrode layer (932), and the magnetically sensitive unit stack layer (1547). This allows the temperatures of regions A, B, and C to be very close, far below the melting points of the top and bottom electrode layers.

[0121] The following describes two main cases of heat-absorbing layers in the magnetoresistive sensor layer structure.

[0122] In the first scenario, the heat-absorbing layer is electrically isolated from the adjacent electrode layer by an insulating layer. The insulating layer is very thin to facilitate heat conduction. In this case, the arrangement of the heat-absorbing layer is not affected by the arrangement of the electrode layers. Specifically, the top heat-absorbing layer is electrically isolated from the top electrode layer; and / or, the bottom heat-absorbing layer is electrically isolated from the bottom electrode layer.

[0123] The second scenario involves the heat-absorbing layer making direct electrical contact with the adjacent electrode layer. This corresponds to the necessary electrical isolation between different heat-absorbing layer regions in the magnetoresistive sensor layer structure, ensuring that adjacent magnetoresistive sensing units do not short-circuit through the conduction of the heat-absorbing layer. The advantage of this scenario is that the heat-absorbing layer directly transfers heat to the electrode layer. Specifically, electrical contact between the top heat-absorbing layer and the top electrode layer corresponds to electrical isolation between different top heat-absorbing layer regions in the magnetoresistive sensor layer structure. And / or, electrical contact between the bottom heat-absorbing layer and the bottom electrode layer corresponds to electrical isolation between different bottom heat-absorbing layer regions in the magnetoresistive sensor layer structure.

[0124] For ease of description, the following embodiments only illustrate the design of the top heat-absorbing layer in the magnetoresistive sensor layer structure. The design principles are equally applicable to the design of the bottom heat-absorbing layer in the magnetoresistive sensor layer structure. It can be understood that the design principles of the first region of the top heat-absorbing layer are the same as those of the fourth region of the bottom heat-absorbing layer; the design principles of the second region of the top heat-absorbing layer are the same as those of the fifth region of the bottom heat-absorbing layer; and the design principles of the third region of the top heat-absorbing layer are the same as those of the sixth region of the bottom heat-absorbing layer.

[0125] When an insulating material is used for electrical isolation between the top heat absorption layer and the top electrode layer, the topology is as follows.

[0126] Figure 4 This is a topological diagram of the top heat-absorbing layer of a magnetoresistive sensor layer structure. The top heat-absorbing layers 13 of two adjacent magnetoresistive sensor layer structures are electrically isolated; in other embodiments, the top heat-absorbing layers of two adjacent magnetoresistive sensor layer structures may be directly connected. The magnetoresistive sensor layer structure includes a pin 100, which is not covered by the top heat-absorbing layer 13. Figure 4 As shown, along the top-to-top direction, the top heat-absorbing layer 13 covers the top electrode layer 7 and the bottom electrode layer 5, and the top heat-absorbing layer 13 and the top electrode layer 7 are electrically isolated; the top heat-absorbing layer 13 includes a first region and a second region, the first region overlaps with the bottom electrode layer 5 but does not overlap with the top electrode layer 7, the second region overlaps with the top electrode layer 7, the space between the top heat-absorbing layer 13 and the top electrode layer 7 is filled with an insulating material, and the first region and the second region are in electrical contact.

[0127] The first region of the top heat-absorbing layer 13 corresponds to region A of the magnetoresistive sensor layer structure, and the second region of the top heat-absorbing layer 13 corresponds to region E of the magnetoresistive sensor layer structure, wherein region E includes regions B and C.

[0128] The top heat-absorbing layer 13 is described in detail by defining regions D and F of the magnetoresistive sensor layer structure. The top heat-absorbing layer region corresponding to the bottom electrode layer 5 is region D of the top heat-absorbing layer 13 corresponding to the magnetoresistive sensor layer structure. The top heat-absorbing layer region corresponding to the top electrode layer 7 is region E of the top heat-absorbing layer 13 corresponding to the magnetoresistive sensor layer structure. Region F, the union of regions D and E of the magnetoresistive sensor layer structure, constitutes the topology of the top heat-absorbing layer 13. Region G is the region not covered by the top heat-absorbing layer 13, the top electrode layer 7, and the bottom electrode layer 5.

[0129] Figure 4 During laser scanning, the corresponding topology may have a difference in thermal conduction between the G region not covered by the top heat absorption layer 13 and the F region covered by the laser, but this does not affect the magnetic field annealing of the magnetoresistive sensing unit array region by the laser.

[0130] Figure 5 for Figure 4 The topology diagram of the top heat-absorbing layer of the single-arm magnetoresistive sensor layer structure is shown. In the magnetoresistive sensor layer structure, the topology of the top heat-absorbing layer, formed by the union of all D and E regions corresponding to the magnetoresistive sensor layer structure, is shown as labeled 130. The topology of all G regions is shown as labeled 140, which is not covered by the top heat-absorbing layer 13, the top electrode layer 7, and the bottom electrode layer 5. The elliptical shape represents the magnetic sensing unit stack layer 6.

[0131] Figure 6 for Figure 4 The topology diagram of the top heat-absorbing layer of the push-pull multi-arm magnetoresistive sensor layer structure. 100 represents the pin. The two magnetoresistive sensing unit arms on the left have antiferromagnetic nailing layers with a magnetization direction of 150, and the two magnetoresistive sensing unit arms on the right have antiferromagnetic nailing layers with a magnetization direction of 160, where magnetization directions 150 and 160 are opposite. The union of the top heat-absorbing layer region above the top electrode layer 7 and the top heat-absorbing layer region above the bottom electrode layer 5 in the magnetoresistive sensing unit array is marked as 170. The top heat-absorbing layer connection region between the magnetoresistive sensing unit arrays is marked as 172. The top heat-absorbing layer region connecting pin 100 is marked as 171. 173 is the region not covered by the top electrode layer 7, the bottom electrode layer 5, and the top heat-absorbing layer 13.

[0132] Figure 7 This is a topological diagram of the top heat-absorbing layer of another magnetoresistive sensor layer structure. The top heat-absorbing layers 13 of two adjacent magnetoresistive sensor layer structures are directly connected. (See diagram below.) Figure 7As shown, the top heat-absorbing layer 13 also includes a third region, which does not overlap with either the top electrode layer 7 or the bottom electrode layer 5, and is electrically contacted with both the first and second regions. 100 is a pin, which is not covered by the top heat-absorbing layer 13. The E region of the magnetoresistive sensor layer structure above the top electrode layer 7 corresponds to the second region of the top heat-absorbing layer 13, the A region of the magnetoresistive sensor layer structure above the bottom electrode layer 5 corresponds to the first region of the top heat-absorbing layer 13, and the G region, not covered by the electrode layer, corresponds to the third region of the top heat-absorbing layer 13.

[0133] Figure 8 for Figure 7 The topology of the top heat-absorbing layer of the single-arm magnetoresistive sensor layer structure is shown. In the magnetoresistive sensor layer structure, the area except for pin 100 is covered by the top heat-absorbing layer 13.

[0134] Figure 9 for Figure 7 The topology of the top heat-absorbing layer of the push-pull multi-arm magnetoresistive sensor layer structure is shown. 100 is the pin, and the area except for pin 100 is covered by the top heat-absorbing layer 13.

[0135] Figure 10 This is a topological diagram of the top heat-absorbing layer of another magnetoresistive sensor layer structure. In the magnetoresistive sensor layer structure, along the bottom-to-top direction, the top heat-absorbing layer 13 covers the top electrode layer 7 and the bottom electrode layer 5. The top heat-absorbing layer 13 and the top electrode layer 7 are in electrical contact, which can reduce the obstacle to heat conduction.

[0136] To avoid short circuits between the stacked layers 6 of the magnetic sensing units, the top heat-absorbing layer 13 includes a first region and a second region. The first region overlaps with the bottom electrode layer 5 but not with the top electrode layer 7, while the second region overlaps with the top electrode layer 7. There is a gap between the top heat-absorbing layers of the first and second regions, and the first and second regions are electrically isolated from each other, achieving mutual electrical isolation between the top heat-absorbing layers above region A and above region B. Furthermore, the pin 100 is not covered by the top heat-absorbing layer 13, and region G of the magnetoresistive sensor layer structure is not covered by the top heat-absorbing layer 13.

[0137] Figure 11 for Figure 10 The diagram shows the topology of the top heat-absorbing layer of a single-arm magnetoresistive sensor layer structure. Pin 100 is not covered by the top heat-absorbing layer 13. At this time, the top heat-absorbing layer above the top electrode layer 7 is 134, and the top heat-absorbing layer corresponding to region A is 135. 134 and 135 are electrically isolated from each other. The area not covered by the electrode layer is marked as 136, and it is also not covered by a heat-absorbing layer above it.

[0138] Figure 12 for Figure 10The topology diagram of the top heat-absorbing layer of the push-pull multi-arm magnetoresistive sensor layer structure is shown. 100 is the pin, which is not covered by the heat-absorbing layer. The top heat-absorbing layer corresponding to the top electrode layer 7 is 137, and the top heat-absorbing layer corresponding to the bottom electrode layer 5 is 138. The area connecting the top heat-absorbing layers between the magnetoresistive sensing unit arrays is marked as 142. The area connecting the pin 100 is marked as 141. 139 is the area not covered by the top electrode layer 7, the bottom electrode layer 5, and the top heat-absorbing layer 13.

[0139] Figure 13 This is a topology diagram of the top heat-absorbing layer of another magnetoresistive sensor layer structure. 100 is a pin, which is not covered by a heat-absorbing layer. The first region of the top heat-absorbing layer 13 corresponds to region A of the magnetoresistive sensor layer structure, the second region of the top heat-absorbing layer 13 corresponds to region E of the magnetoresistive sensor layer structure, and the third region of the top heat-absorbing layer 13 corresponds to region G of the magnetoresistive sensor layer structure that is not covered by the electrode layer. The third region is electrically isolated from the first and second regions, respectively, or the first and third regions are combined and electrically isolated from the second region.

[0140] Figure 14 for Figure 13 The topology diagram of the top heat-absorbing layer of the single-arm magnetoresistive sensor layer structure is shown. 100 is the pin, which is not covered by the heat-absorbing layer. At this time, the top heat-absorbing layer above the top electrode layer 7 is 151, the top heat-absorbing layer above the bottom electrode layer 5 is 152, and the top heat-absorbing layer above the area not covered by the electrode layer is 153. The top heat-absorbing layers 152 and 153 form a union to constitute the top heat-absorbing layer 154. 154 and 151 are electrically isolated from each other.

[0141] Figure 15 for Figure 13 The topology diagram of the top heat-absorbing layer of the push-pull multi-arm magnetoresistive sensor layer structure is shown. 100 is the pin, which has no heat-absorbing layer above it. The top heat-absorbing layer above the top electrode layer is 161. The area connecting the top heat-absorbing layers between the magnetoresistive sensing unit arrays is marked as 164. The area connecting the top heat-absorbing layer to pin 100 is marked as 165. The top heat-absorbing layer above the bottom electrode layer is 162. The corresponding top heat-absorbing layer above the area not covered by the electrode layer is 163. 162 and 163 are combined to form the top heat-absorbing layer region 166. The top heat-absorbing layer region 166 and the top heat-absorbing layer region 161 are electrically isolated.

[0142] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A magnetoresistive sensor layer structure for laser annealing, characterized in that, include: Substrate; A magnetoresistive sensing unit located on the substrate, the magnetoresistive sensing unit comprising, from bottom to top, a seed layer, a bottom electrode layer, a magnetic sensing unit stack layer and a top electrode layer, the magnetic sensing unit stack layer comprising at least an antiferromagnetic nailing layer or a permanent magnet bias layer; The top heat-absorbing layer located above the magnetoresistive sensing unit and / or the bottom heat-absorbing layer located below the magnetoresistive sensing unit, wherein the volume of the top heat-absorbing layer is... Specific heat The product of densities is greater than the volume of the top electrode layer. Specific heat The product of densities, the volume of the bottom heat-absorbing layer Specific heat The product of densities is greater than the volume of the bottom electrode layer. Specific heat The product of densities means that when the writing temperature of the antiferromagnetic nailing layer or the permanent magnet bias layer is higher than their respective blocking temperature or Curie temperature, the temperatures of the bottom electrode layer and the top electrode layer are both lower than their respective melting point temperatures. A laser absorption layer is located above the magnetoresistive sensing unit; A laser-transparent layer is located above the laser-absorbing layer; Along the top-to-bottom direction, the top heat-absorbing layer covers the top electrode layer and the bottom electrode layer, and the top heat-absorbing layer and the top electrode layer are electrically isolated from each other; the top heat-absorbing layer includes a first region and a second region, the first region overlaps with the bottom electrode layer but not with the top electrode layer, the second region overlaps with the top electrode layer, an insulating material is filled between the top heat-absorbing layer and the top electrode layer, and the first region and the second region are in electrical contact; the top heat-absorbing layer also includes a third region, the third region does not overlap with either the top electrode layer or the bottom electrode layer, and the third region is in electrical contact with both the first region and the second region; Alternatively, along the bottom-up direction, the top heat-absorbing layer covers the top electrode layer and the bottom electrode layer, and the top heat-absorbing layer is in electrical contact with the top electrode layer; the top heat-absorbing layer includes a first region and a second region, the first region overlaps with the bottom electrode layer but does not overlap with the top electrode layer, the second region overlaps with the top electrode layer, and the first region and the second region are electrically isolated from each other.

2. The magnetoresistive sensor layer structure according to claim 1, characterized in that, The substrate surface facing the magnetoresistive sensing unit has a passivation layer, the thermal conductivity of which is less than that of the seed layer. 1 / 10.

3. The magnetoresistive sensor layer structure according to claim 1, characterized in that, The top heat-absorbing layer is electrically connected to the top electrode layer. The top heat-absorbing layer also includes a third region, which does not overlap with either the top electrode layer or the bottom electrode layer, and is electrically isolated from both the first region and the second region.

4. The magnetoresistive sensor layer structure according to claim 1, characterized in that, Along the bottom-to-top direction, the bottom heat-absorbing layer covers the top electrode layer and the bottom electrode layer, and the bottom heat-absorbing layer and the bottom electrode layer are electrically isolated from each other; The bottom heat-absorbing layer includes a fourth region and a fifth region. The fourth region overlaps with the bottom electrode layer but does not overlap with the top electrode layer. The fifth region overlaps with the bottom electrode layer. An insulating material is filled between the bottom heat-absorbing layer and the bottom electrode layer. The fourth region and the fifth region are in electrical contact.

5. The magnetoresistive sensor layer structure according to claim 4, characterized in that, The bottom heat-absorbing layer further includes a sixth region, which does not overlap with either the top electrode layer or the bottom electrode layer, and is electrically in contact with both the fourth region and the fifth region.

6. The magnetoresistive sensor layer structure according to claim 1, characterized in that, Along the bottom-to-top direction, the bottom heat-absorbing layer covers the top electrode layer and the bottom electrode layer, and there is an electrical contact between the bottom heat-absorbing layer and the bottom electrode layer; The bottom heat-absorbing layer includes a fourth region and a fifth region. The fourth region overlaps with the bottom electrode layer but does not overlap with the top electrode layer. The fifth region overlaps with the bottom electrode layer. The fourth region and the fifth region are electrically isolated from each other.

7. The magnetoresistive sensor layer structure according to claim 6, characterized in that, The bottom heat-absorbing layer further includes a sixth region, which does not overlap with either the top electrode layer or the bottom electrode layer, and is electrically isolated from both the fourth region and the fifth region.

8. The magnetoresistive sensor layer structure according to claim 1, characterized in that, The material of the top heat-absorbing layer or the bottom heat-absorbing layer is tantalum, titanium, copper, molybdenum, gold, silver, aluminum, platinum or tin.

9. The magnetoresistive sensor layer structure according to claim 1, characterized in that, The laser absorption layer is made of carbon black, or a non-magnetic laser-absorbing resin containing carbon black, or a laser-absorbing coating.

10. The magnetoresistive sensor layer structure according to claim 1, characterized in that, The material of the laser transparent layer is ZrO2, Ti3O5, Ta2O5, HfO2, ZnS, ZnSe, Al2O3, MgO, MgF2, SiO2, YbF3 or AlF3.

Images